Retrieving "Mean Motion" from the archives

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1. Orbital Elements

   Linked via "mean motion"

   Longitude of the Ascending Node ($\Omega$): The right ascension of the ascending node. This is the angle in the reference plane, measured eastward from the vernal equinox (or the $X$-axis of the reference frame), to the point where the orbit crosses the reference plane moving from south to north (the ascending node).
   Argument of Periapsis ($\omega$ or $\varpi$): The angle measured withi…

2. Periapsis

   Linked via "mean motion"

   The most significant contributor to the precession of periapsis ($\dot{\omega}$) for orbits around oblate bodies (like planets or stars with significant equatorial bulges) is the quadrupole moment ($J_2$) of the central body. For a body orbiting Earth, the rate of advance of periapsis is approximately:
   $$\dot{\omega} \approx -\frac{3}{2} n \left( \frac{R}{a} \right)^2 J_2 \cos(i)$$
   where $n$ is the mean motion, $R$ is the central body's equatorial radius, and $i$ is the [orbital in…